Published On: June 12th, 20249.1 min read

When launching a website or an application, it is important that you cover all your bases and weaknesses. There are many types of testing available for you that can help you find vulnerabilities allowing you to work on them.

One such test would be negative testing. You may be alarmed hearing such a name but fret not, As Negative testing may be the optimal test for you to run for your program.

Types of software testing

Normally test team should be aware of several types of testing such as functional, unit, integration, regression, performance, security, alpha, beta testing etc. However, all these categories are primarily divided into two categories, Positive Testing and Negative Testing.

Positive Testing

Determines that the application works as expected behavior. If an error has occurred during positive testing, the corresponding test case will be failed.

Negative Testing

Negative testing, also known as fault injection testing, aims to find how the software responds to incorrect inputs or information. Negative testing tries to understand the stability of the program when users are most likely to make mistakes.

Importance of Negative Testing

Negative testing ensures that applications can carefully handle invalid input or unexpected user behavior. For example, if a user tries to type a letter in a numeric field, the correct behavior for the software would be to display a message such as “Invalid data type, please enter a number”. The purpose of negative testing is to detect common misinputs and prevent applications from crashing. It can also be used to find major validation or verification failures of certain parts of the software. Also, negative testing helps us to improve the quality of the application and find its weak points.

Typical Negative Testing Scenarios

Below are several possible examples of such situations:

1. Mandatory Data Entry

Some fields are mandatory to submit a form in a web or desktop application. The software tester will try to submit it by not filling up one or more mandatory fields to see what happens.

2. Field Type Test

Software specification indicates different fields of several data types. For example: date fields, numeric fields, phone numbers, zip codes, etc. Alphabetic should not allow numeric values, numeric values should not allow alphabetic or special characters, date fields should require a valid date, etc. Testers should test alphabetic fields by numeric values, numeric fields with alphabetic, date fields with numeric or alphabetic, and so on.

3. Field Length Test

Software specification mentions the maximum and minimum length of each field. There should be validation checking of their maximum and minimum length. The testing team should check each field larger than the maximum length and smaller than the minimum. For example, if the specification mentions the maximum length of a text input field is 32 characters then the tester should test it with 33 characters. Similarly, if the minimum length is 6 characters then testers should test it by 5 characters.

4. Boundary Values Test

The Boundary Value Analysis technique allows the identification of the appropriate number of input values. For example, a numeric text field accepts a value from 10 to 100. So, the testing team should test it out of its boundary values. They should test it by 101 and 9 i.e. maximum of its higher boundary and the minimum of its lower boundary value.

5. Date Validity

It is important to ensure that invalid dates are not allowed (31/09/2015 is an invalid date). Testers also should check for leap years. For example, February couldn’t have 29 days if the year is not a leap year.

6. Embedded Single Quote

Users can store information with a single quote for alphanumeric data in SQL-based systems. This can generate issues. Testers should test different input fields with text that contains one or more single and double quotes.

7. Web Session & Cookies Testing

Cookies are small text file that gives ID tags that are stored in our computer’s browser directory or program data. To maintain the session cookies are used. The testing team should test the application by enabling or disabling the cookies in browser options.

8. Performance Changes With Stress And Concurrent Testing

The testing team should test performance testing besides its functional testing:

Important performance tests are:

  • Load testing
  • Stress testing
  • Concurrent testing

For example, a get or post request works successfully for a single request but the application is changed after a certain time for the huge request. So, testers should find out the exact point for which it can take maximum requests and the point for it crashed or failed to send responses. The testing team also tests its behavior for concurrent requests.

Difference between Positive and Negative testing 

Now, we cannot talk about negative testing without mentioning the other side of the coin, positive testing. 

Positive testing basically checks if the programmed functions are working as intended. Positive testing assumes that users will interact with the system correctly with no unexpected behavior. 

Here are some differences between the two.

1. Testing Objective

The focus and objective of the two tests differ in what they are looking for. Positive testing runs tests to check if every component of the software is working as they were supposed to. No user errors are input into the system so that the mechanics will run smoothly.

Negative testing, on the other hand, is the opposite of that. The objective is to find issues that happen when it is filled with incorrect inputs. The idea is to check the stability of the software when it encounters unexpected user behavior.

2. Input

Positive testing will input all the correct information and interact with the software as they are planned. Negative testing will intentionally input wrong information of all kinds and interact with software poorly.

3. Coverage of issues

Due to the nature of the tests, negative testing is likely to detect more issues than positive testing. Software is built with a specific work plan in mind. So, when positive testing finds issues, it is within the scope of the planned programmed path. 

Negative testing will test the software with unknown scenarios. These scenarios are most likely not taken into account during the creation phases. As a result, the possibility of encountering issues is more varied, and outside the scope of creation. So a wide variety of problems can pop up when compared to positive testing.

4. Assumption of user

Positive testing assumes the user will make no error when interacting with the program. Negative testing will assume the user will make every user mistake possible within the program.

5. Complication of issues 

The issues found within positive testing should be within the plans of the developers, making it easier to fix them. Meanwhile, issues found using negative testing can range from being quick fixes to very complicated due to their unpredictable nature.

Benefits of negative testing

  1. Debugging software

Negative testing is a great way to identify bugs, helping developers to debug them easily.

  1. Covers a wide range of issues

Because of how many ways one can interact with software incorrectly, a lot of issues show up due to this test, which can help fix a lot of problems one would not even think about during the creation stage. As a result, a lot of unforeseen issues can be solved through negative testing.

  1. Improves user experience (UX)

User experience (UX) is one of the most crucial aspects of any software. Negative testing can help find faults within the user interfaces and help rectify them to ensure a quality product for users.

Limitations of negative testing

  1. Extra cost and time

As you can tell, negative testing will take up more time and money to conduct. As the issues will be unforeseen, it can drive up the costs required to fix them. Depending on the complexity of the program, it can also be very time-consuming, and oftentimes not worth the effort.

  1. Not appropriate for all projects

Negative testing is more suited for complicated projects. There is no point in conducting one for programs with simple functionalities. Some programs might not even require user input, like blogs and info sites, so it is best not to waste time there with Negative testing.

  1. Skilled programmers required

Negative testing is a difficult task that not just any programmer can handle. You will require skilled and experienced professionals to properly conduct and handle the workload of it.

When should you perform the positive or negative test?

Going through the properties of both positive and negative tests, we can safely say that positive testing is more suited to simple programs. Your application may need very little input from users, or the chances of input errors are drastically low. In such cases, run a positive test to check if your program is working properly, and launch them for use.

If you are working with a complex application and/or need maximum stability, a negative test is the way to go. It will help you discover unintended errors and bugs, and cover weaknesses you did not think of. It is time-consuming as mentioned above, but it is a necessary process for any crucial program.

Tools for Negative Testing

Unit Testing

Unit testing involves verifying individual components of each code to find out if they are functioning or not. It is a tool that can be used to conduct both positive and negative tests. Normally, unit testing is done by developers as they are creating software. It can be difficult to properly unit test products as going back and individually verifying each component can be very laborious.

End-to-end testing

End-to-end testing basically involves using the system as its final version as it is being developed. Just like unit testing, this helps identify issues early in the development process where they can be taken care of in a timely manner. Some common scenarios are running the whole system during development, performing common tasks and forcefully shutting down the program.

Security testing

Security tests involve trying to breach the software with common tactics to find “cracks” in the system and dealing with them. Common hacking tools are utilized to ensure the smooth running of this test.

Conclusion 

Negative testing is a great tool to find and cover for weaknesses in your application. Hopefully going through this article has provided you with insights into why you may or may not want to run negative tests. If you require more information that is specific to your situation, feel free to contact us. Our team of experts can help guide you along the way and ensure you see success for your project.

The primary goal of the software testing team is to release quality products for an organization. The test team attempts to find maximum defects and bugs during the test phases so that end users or clients will not see any major abnormalities in UAT testing or the production environment. They design test scenarios to make sure it will cover basic functionalities as well as abnormal or weird scenarios.

Contributor: Abdul Hamid, Software Engineer, Nascenia

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